Trimethylolalkanes are useful as a raw material of alkyd resins, polyurethane resins, (un)saturated polyester resins, synthetic lubricants, surfactants, reactive monomers, and the like.
Trimethylolalkanes may be prepared through hydrogenation of dimethylolalkanes (hereinafter, called methylol alkanal). A process of preparing methylol alkanal by reacting formaldehyde and alkyl aldehyde in the presence of an amine based catalyst is generally performed in one batch type process (See FIG. 2).
A yield of methylol alkanal is determined by a molar ratio of added formaldehyde and alkyl aldehyde. To increase selectivity of methylol alkanal, formaldehyde is used in an excess amount of a theoretical minimum molar ratio or more.
However, formaldehyde used as a raw material is used as an aqueous solution having a purity of approximately 30% to 42% due to properties thereof. Therefore, the amount of wastewater after reaction increases as much as the amount of formaldehyde used in an excess amount. In addition, since it is difficult to isolate entire formaldehyde included in methylol alkanal, an amount of formaldehyde remaining in methylol alkanal may function as a catalyst poison in hydrogenation when methylol alkanal is hydrogenated.